One complication for the backyard ADU business is that zoning rules vary among municipalities and neighborhoods. ....

"They’re promoted by cities like Arvada [Colorado] as a way to help with the affordable housing issue and the issue of housing the aging population, which are both coming together pretty strongly right now," Kephart says.

In Denver, ADUs are allowed only in neighborhoods zoned for mixed use, such as Stapleton...

Other basics:

price: $75,000 - $200,000

size: 400 - 1160 square feet

owner Michael Kephart launched Sidekick Homes early this spring

The best part:

They're ... pre-built and trucked from the factory to the home site with everything from the ceiling fixtures to the kitchen counters intact.